1. Field of the Invention
This invention relates to an interconnection structure for a semiconductor integrated circuit having polycrystalline silicon interconnections and metal interconnections.
1. Description of the Prior Art
A semiconductor integrated circuit having polycrystalline silicon interconnections and metal interconnections is described in, for example, "MOS Integrated Circuits" edited by William M. Penney and Lillian Lau in "Microelectronics Series" published by Van Nostrand Reinhold Company. Wiring in such a circuit is effect as stated below. Polycrystalline silicon interconnections which contain impurities at a high concentration are provided in predetermined regions on a first insulating film on a semiconductor substrate which forms a semiconductor body including transistors therein. A second insulating film, and metal interconnections in a direction intersecting the polycrystalline silicon interconnections are provided on the polycrystalline silicon interconnections. The necessary contacts or connections between the metal interconnections and the polycrystalline silicon interconnections are made through through-holes provided in the second insulating film in correspondence with the intersecting parts of the different interconnections.
According to this expedient, for providing the through-holes, portions which are several microns larger than the contacts between the different interconnections must be formed in the polycrystalline silicon interconnections of the high impurity concentration on account of mask alignment tolerances. This lends to the disadvantage that the interconnection pitch cannot be made small.